FIG. 9 shows an antitheft system conventionally used in stores wherein commodities such as compact disk cassettes and magnetic tape cassettes are on display for sale, to protect these articles from shoplifting or like illegal acts.
The antitheft system comprises an antitheft gate 3 installed in the vicinity of an exit 30 of the store, and an alarm unit 2 attached to a commodity 5. The antitheft gate 3 has a circuit board 31 and a transmitting antenna (not shown). The circuit board 31 is provided with a transmitting circuit (not shown) for producing an alarm activating signal for the alarm unit 2.
With reference to FIG. 10, the alarm unit 2 comprises a buzzer 21, circuit board 27, battery (not shown), etc. which are housed in a casing 20. The casing 20 has a surface formed with sound emitting holes 28 and an alarm actuating switch piece 22. The buzzer 21 has its operation controlled by the circuit board 27 and is adapted to produce an alarm when the unit 2 is removed from the commodity or when the unit 2 passes by the antitheft gate 3.
The commodity is placed on display in the store, with the alarm unit 2 attached thereto. When selling the commodity to the customer, the clerk holds the buzzer 21 out of operation by s ending a specified signal to the circuit board 27 of the alarm unit 2, then removes the unit 2 from the commodity and hands the commodity to the customer in exchange for money.
If the customer wrongfully removes the alarm unit 2 from the commodity 5, the switch piece 22 is turned off to actuate the buzzer 21. Further if the customer acts to unlawfully bring the commodity 5 out of the store along with the alarm unit 2, the circuit board 27 of the alarm unit 2 receives an alarm activating signal from the transmitting antenna of the antitheft gate 3 to turn on the buzzer 21.
However, the antitheft system described involves the likelihood that when selling the commodity 5, the clerk will inadvertently hand the commodity 5 to the customer without removing the alarm unit 2 therefrom. A problem then arises in that the buzzer 21 goes on when t he customer passes by the antitheft gate 3 although purchasing the commodity lawfully, giving discomfort to the customer.